This invention relates to commutator valves for hydraulic devices of the expanding-contracting pocket type, such as hydraulic motors. Specifically, it relates to an assembly of plate members adapted to be fixed together to form a commutator valve for a device such as a hydraulic motor. In particular, it relates to a single set of plate members which when assembled in one relationship effect rotation of the motor in one direction, and when assembled in another relationship effect rotation of the motor in a reverse direction without changing the high or low pressure ports of the motor.
A known commutator valve construction for a hydraulic motor is shown in U.S. application Ser. No. 706,131 now U.S. Pat. No. 4,087,215. The commutator valve is formed by three plate members which are brazed together. The plate members include a pair of end plates, and a specially formed central plate. The central plate controls the flow of fluid in such a manner that the valve directs high pressure fluid from a high pressure inlet port to expanding pockets and directs low pressure fluid from contracting pockets to a low pressure outlet port to rotate an output shaft in one direction.
One way of reversing the direction of rotation of the output shaft of the motor is to reverse the ports, i.e., to direct high pressure fluid to the previous outlet port and low pressure fluid from the previous inlet port.
Another way of reversing the direction of rotation of the output shaft of the motor is to vary the commutator valve construction. This could be accomplished by varying the construction of the central plate depending upon the direction of rotation desired.
The present invention provides a unique assembly of plate members which are designed to be assembled and fixed together to form a commutator valve for hydraulic devices such as hydraulic motors. In the preferred embodiment a single set of plate members are assembled in one of two different alignments to form the commutator valve, depending upon the desired direction of rotation of the output shaft of the motor.
Thus, constructing a commutator valve according to the present invention avoids the necessity of either reversing the high and low pressure ports for reversing the direction of rotation of a motor, and also avoids the necessity of forming specially constructed commutator valve parts for this purpose.
The assembly of plate members includes a first end plate, a second end plate and a plurality of intermediate plates disposed therebetween. The first end plate includes first and second arrays of fluid passageways for communicating with expansible and contractable pockets, respectively, during operation of the device. The intermediate plates are designed such that in a first alignment they direct high pressure fluid from the high pressure port to the first array of passageways and low pressure fluid from the second array of passageways to the low pressure port. In a hydraulic motor, they direct fluid to cause the output shaft to rotate in one direction. In a second alignment the intermediate plates direct high pressure fluid from the high pressure port to the second array of passageways and low pressure fluid from the first array of passageways to the low pressure port. In the second alignment, they direct fluid to cause the motor output shaft to rotate in a reverse direction. Certain of the plates have indicia for identifying which alignment the plates are assembled in.
The end plates and intermediate plates are preferably thin, and of equal thickness. Thus, the single set of plate members can be stamped from sheet metal stock from the same heat. This is believed to enhance the compatibility of the plates for being brazed together to form the commutator valve.